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From: bruno vieira da silva <[email protected]>
To: [email protected]
Subject: Query planning read a large amount of buffers for partitioned tables
Date: Wed, 15 Jan 2025 13:29:30 -0500
Message-ID: <CAB+Nuk9NAH8MxDK9ng9G+Vvs8XAaaV7Jc=F7FWrbF8U8WWaDEw@mail.gmail.com> (raw)

Hello All.

On pg 17 now we have better visibility on the I/O required during query
planning.
so, as part of an ongoing design work for table partitioning I was
analyzing the performance implications of having more or less partitions.
In one of my tests of a table with 200 partitions using explain showed a
large amount of buffers read during planning. around 12k buffers.

I observed that query planning seems to have a caching mechanism as
subsequent similar queries require only a fraction of buffers read during
query planning.
However, this "caching" seems to be per session as if I end the client
session and I reconnect the same query execution will require again to read
12k buffer for query planning.

Does pg have any mechanism to mitigate this issue ( new sessions need to
read a large amount of buffers for query planning) ? or should I mitigate
this issue by the use of connection pooling.
How is this caching done? Is there a way to have viability on its usage?
Where is it stored?

Thanks
-- 
Bruno Vieira da Silva

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